The conventional displacement measurement systems for cantilever(s) in a scanning force microscope include:
(1) the optical lever system;
(2) the homodyne interferometer system using an end face of an optical fiber;
(3) the Fabry-Perot homodyne interferometer system using a concave lens;
(4) the heterodyne laser Doppler meter system; and
(5) the homodyne interferometer system that reflects reference light using only a plane mirror without employing any focal lens.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2003-114182
[Patent Document 2] WO 2004/017329
[Non-patent Document 1] J. Yang et al., “Ultra-small single crystal silicon cantilevers for a new generation of SFM”
[Non-patent Document 2] Hans J. Hug et al., “Scanning Force Microscopy with Ultrasmall Cantilevers”